Adoptive T cell therapy in the form of allogeneic blood and marrow transplantation (BMT) has proven to be one of the few curative treatments for hematological malignancies. Mature donor T cells in the donor inoculum play a central role in mediating graft-versus-tumor (GVT) responses against residual tumor cells that persist after conditioning regimens, and also in facilitating donor immune reconstitution. However the full exploitation of this clinical intervention is greatly limited by the occurrence of graft-versus-host disease (GVHD), which remains one of the main complications of BMT. Acute GVHD is characterized by severe, and potentially lethal, tissue damage to the skin, liver, gastrointestinal tract and lymphoid tissues of transplanted patients, mediated by donor T cells responding to host alloantigens. The homing of T cells to GVHD target organs and their regulation via integrins, selectins and chemokine receptors has therefore been recognized as potential novel sites for intervention to ameliorate or prevent GVHD while still allowing GVT effects. T cell trafficking and homing involves a compendium of events, that require the expression of specific adhesion molecules and chemokine receptors on the T cell surface, along with the spatial and temporal manifestation of their ligand counterparts on high endothelial venules (HEV) of inflamed tissues. Indeed, a number of studies focusing on the manipulation of the [unreadable]7 chain expression of the a4[unreadable]7 integrin (an intestinal homing receptor expressed on the surface of T cells) found decreased infiltration of donor T cells to the host gut epithelium, which in turn was associated with decreased intestinal tissue damage in various GVHD murine models. The clinical translation of these studies is however hindered by the lack of an available approach that could safely and efficaciously manipulate T cells in the donor hematopoietic stem cell inoculum, to downregulate their expression of a4[unreadable]7 integrin. The proposed studies will thus focus on the use of small-hairpin RNA (shRNA) to test the hypothesis that stable knockdown expression of the [unreadable]7 integrin chain of donor T cells via lentiviral infection, prior to transplant, can provide long-term reduction of GVHD severity without affecting the beneficial GVT potential of those donor T cells. The immune functionality and cell adhesion capabilities of [unreadable]7-shRNA-transduced human T cells will also be assessed, as a first step towards translation of the proposed methodology to the clinical setting. PUBLIC HEALTH RELEVANCE: Graft-versus-host disease (GVHD) still remains one of the main complications associated with bone marrow transplantation (BMT), a well accepted treatment for a number of blood malignancies. In the current study we will investigate the implementation of novel genetic techniques to redirect donor T cells (the causal entities of GVHD) away from inflicting damage to the patient's organs (the hallmark of GVHD). This approach will open up a number of possibilities for new and potentially less aggressive therapeutic strategies for BMT. More importantly, the results from the proposed study could increase the number of donors for BMT, because transplanted T cells would be engineered to infiltrate less into the organs where they can cause undesirable harm upon encountering differences between themselves and the host cells;a situation that occurs specially when the donor cannot be fully matched.